If we are observant(善于观察的), we can find that most of the flowers in nature are red, orange and yellow. If we have seen a black flower, it is a chance in a million. People have made census (统计) to colors of more than four thousand kinds of flowers and discovered that only eight of them are black. Why are black flowers so rare?

    As we know, sunlight is formed by seven different kinds of colored light. The wave length of each light changes, so the quantity of heat in each light changes, too. Flowers, especially their petals (花瓣) , are very weak and easy to the harm caused by high temperature. Black flowers can take in all the light waves, which cause the flowers to dry up in a high temperature. So the black flowers can hardly continue their lives. While red flowers, orange flowers and yellow ones can protect themselves from sunlight by reflecting（反射） the red light, orange light and yellow light, each of which has a large quantity of heat.

    That is why red, orange and yellow flowers are very common in nature while black flowers are so unusual.

    When you're having a hard time with your homework or when you're preparing for your term paper, these student-focused websites can help you with just about anything you need. The key to getting the most out of these online resources is to know how they can best be used to your advantage.

Facebook

    Although Facebook can be one of your biggest time-wasters and distractions when you are supposed to be getting work done, it can also be one of your most valuable resources. Most of your classmates will probably have a Facebook account, so anyone you need to connect with about a class you missed or about a problem is usually just a few clicks away.

SparkNotes

    With a free library of history timeline, philosophy study guides and library summaries, SparkNotes has covered just about any reading-related jam you find yourself in. Just run a search for the book, play, or short summary of the material you are supposed to read.

Amazon.com

    Do you finish every term with many expensive textbooks you will never open again? Instead of letting the money spent go to waste, get back some of your cash by selling your books on Amazon.

RateMyProfessors.com

    Choosing new classes can sometimes be like trying to pick out your clothes in the dark, a total guessing game. Which teacher gives out the hardest problem sets? How much homework will that history professor give you every week? At RateMyProfessors.com, students all over the country rate their professors on quality, helpfulness, and how hard their classes are.

 Wikipedia

    While Wikipedia isn't aimed specifically at students, it is difficult to think of another website that does more to reduce the pain of paper writing and researching. Wikipedia gives you a quick way to find sources and get the details of almost any topic you need to research — all without walking to the library.

    If Frida Kahlo（1907-1954） is today one of the best-known and most popular figures of 20th-century, Mexican art, it is undoubtedly because of her personality and the originality（独创性）of a body of works. Her work is, above all, the expression of a real life－a tragic and stormy life, one that challenged all conventions. The mere mention of her name excites enthusiasm and admiration, but her work is rarely exhibited, and has not been shown in France for fifteen years. The selection to go on show at the Musee de L'Orangerie includes major works by the artist, with masterpieces from the Museo Dolores Olmedo.

    The life and work of Frida Kahlo cannot be separated from those of her companion Diego Rivera（1886-1957）. Together they became figures of legend, and both have a place in the pantheon of 20th-century Mexican artists. Famous for his large wall paintings, Rivera's easel paintings, drawings and prints, which form a large part of his artistic production, are less well-known to the public in Europe. The exhibition aims to trace his artistic career from the early Cubist images, revealing his links with the Paris artists whose works are a key element in the Orangerie collections, to the paintings that established him as the founder of the 20th-century school of Mexican art. His travels throughout Europe influenced his vision and his skills without ever distancing him from his roots, thus confirming his place in history as the founder of the nationalist school.

    The exhibition devoted to the legendary couple Diego Rivera and Frida Kahlo presents their works together, as if to confirm the impossibility of their divorce that was in fact finalized（定下来）but reconsidered after just one year apart. It also gives us a better view of their respective artistic worlds, so different and yet so complementary（互补的）, through the deep-rooted attachment they shared to their country.

    An article describing the attitude of post-1990s generations toward life has recently gone viral on Chinese social media, which resonates with(引起共鸣) millions of youngsters for reflecting their casualness and calmness under gradually increasing social pressure.

    The article was first published on WeChat with the title of “The first group of post-90s generation who have become monks”. By using the phrase “Buddha-like youngsters”(佛系青年), it claimed that some of the post-90s generations, who were born between 1990 and 1992, have “seen through the emptiness of life” and kept a casual and calm attitude toward career and life.

    “It's fine to have something or not and there is no need to pursue or win anything," said the article, while defining "Buddha-like" people and clarifying that the phrase has nothing to do with the religion of Buddhism. An easy example is that Buddha-like youngsters do not care about taking which way to return home or choosing what to eat for lunch, according to the article.

    The phrase has touched the nerves of the Chinese youngsters who are facing the fast-paced life, cut-throat world of career and great mental pressure in China, read a commentary by People's Daily on Wednesday. The phrase was well received by Chinese netizens; the original WeChat post has been viewed by more than 1 million times and then read more than 60 million times on SinaWeibo by Wednesday.

    “The phrase properly describes the mentalities and lifestyle of (some of) the post-90s generations in China, who have become less ambitious and more casual toward life due to the great pressure and fierce competition in today's China”, one SinaWeibo user commented.

    Are you a Buddha-like youngster？

    Bees may soon need to add protein shakes to their diet. Pollen (花粉) normally provides their protein (蛋白质). But rising levels of carbon dioxide (CO₂) in the air have reduced the protein in pollen. That's what a new study finds.

    Scientists compared recently collected flowers from Canada goldenrod. Then they compared pollen in them to pollen in goldenrod reserved at a museum in Washington, DC. They found today's plants have less protein. Protein levels in pollen from the older flowers were 18 percent. Today's goldenrod pollen has only about 12 percent protein. That's about one-third less than 172 years ago. Over that same period, CO₂ levels have gone up by more than one-third. Back more than 170 years ago, they were about 280 parts per million in air. Today they are about 398 ppm.

    To test whether CO₂ changes had played a role in the falling protein levels, the researchers did some tests. They grew goldenrod for two years at CO₂ levels of up to 500 ppm. More CO₂ in the air led to lower levels of protein in the flowers' pollen.

    Joan Edwards, one of the researchers, says that this drop in pollen protein could affect a bee's diet and health. It would be like eating junk food, tasting good but offering less nutrition (营养).

    Honeybees need to eat lots of protein. They use it to feed their young. They also need it to keep their immune systems healthy, says Cédric Alaux, a bee biologist at the French agricultural research agency.

    Bee populations have been decreasing worldwide in recent years. A drop in their food quality might play a role, Edwards says. And that drop might affect crops too. "The health of the bee population is not just for the flowers and the bees and biodiversity." She worries it also could play a role in "human health and well-being."

    A week ago at Compton Elementary School, Georgia, something wonderful happened. Band students from Hillgrove High School arrived to hang out with and talk to the little guys. They wanted to make sure the school's youngest had food in their homes that week.

    The thing that thrilled people was that this generous idea came from 17-year-old Nathan Jones, not an adult. Jones is a good trumpet (小号) player with the Hillgrove Hawks band. The idea, he said, came to him two years ago during a discussion about community service in a freshman leadership class. Serving the community was nothing new to Jones. For years, he and his family, who recently moved from Orlando, Florida, had been active community volunteers.

    Last year, Jones thought it was a good idea to get the school band involved in community service, only for the young kids in the school. Band director Patrick

    Erwin agreed but decided they had neither the time nor the resources to do it. "It got put on the back burner," Jones said. "This year, I decided to try again." This time, Erwin encouraged Jones to take charge and he did.

    Back in August, Jones challenged the band to raise $5, 000 to help with the cost of packing the meals. Within two weeks, they'd collected $6, 000 in donations, enough to provide 2,500 family meals, including bags of rice, soy protein, vitamins and vegetables. By the end of the month, when poor families are struggling, a bag of food can mean the difference between a full stomach and an empty one for many of those students.

    But HiHgrove's effort isn't just about feeding the body. It's about feeding souls, too.

    Early on, the band's goal was to direct students' focus from getting "likes" on social media to building relationships with the people around them. So the band decided on the message, "What the world needs now is love, not likes" for its half-time show.

    "That means actually going into the community and actually showing love," Jones said. "We're going out and doing what we're telling people to do."